Wow… Are you lucky. There is no real fix for this one except to have a tile guy back and repolish the countertops. It will be really messy and unfortunately expensive to do this job. If it helps, sometimes this can be covered under your homeowners policy.

Your only recourse (that sure works) is to have the countertops replaced or have them regrinded and repolished. Either of the two are costly options for a good reason and that is achieving success is slim if you do not have the right tools, skill and experience. So you are not up to the job, do your countertops and wallet a favor by not wasting time and money.

Part of granite counters maintenance is having them resealed once a year or so, if you already have contracted a qualified contractor to work on this, he can be a good candidate to regrind and repolish the countertops. Or if you were satisfied with the quality of work the installer delivered, call him.